hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Is troubleshooting an OSPFv2 issue where a router…
A network engineer is troubleshooting an OSPFv2 issue where a router R1 is not receiving a specific route for 10.0.0.0/8 from a neighbor R2. The adjacency is FULL, and 'show ip ospf database' on R1 shows the LSA for 10.0.0.0/8 as a type 5 LSA. However, the route is not in the routing table. 'show ip route 10.0.0.0' shows no route. What is the most likely cause?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The router R1 has a distribute-list applied to the OSPF process that filters the route 10.0.0.0/8.
If the LSA is in the database, the route should be installed unless there is a filtering mechanism or a routing table issue. One common cause is that the router has a route map that filters the route from being installed. Another possibility is that the router has a static route that is being preferred, but the stem says no route is present. The most likely cause is that the router has a distribute-list that filters the route.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The router R1 has a distribute-list applied to the OSPF process that filters the route 10.0.0.0/8.
Why this is correct
A distribute-list can prevent a route from being installed in the routing table even if the LSA is in the database.
- ✗
The route is a type 5 LSA, but the router is in a stub area.
Why it's wrong here
Stub areas block type 5 LSAs, so the LSA would not be in the database.
- ✗
The router has a higher administrative distance for OSPF routes, causing it to prefer another routing protocol.
Why it's wrong here
If there were another route, it would appear in the routing table; the stem says no route is present.
- ✗
The route has a metric of 16777214, which is considered infinite.
Why it's wrong here
A metric that high would still be installed, but the router would not use it; however, the route would appear in the routing table as a candidate.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
Introduction to ENARSI Exam and Network Fundamentals
Key term
ACL for Routing Protocols
An ACL for Routing Protocols is a set of rules used to filter routing updates between routers, controlling which network routes are advertised or accepted to improve security and stability.
Key term
Policy Based Routing
Policy Based Routing (PBR) is a technology that allows network traffic to be forwarded based on user-defined policies rather than just the destination IP address in the routing table.
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Same concept, more angles
1 more way this is tested on 300-410
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer is troubleshooting an OSPFv3 issue where a router R1 is not learning routes from a neighbor R2. The adjacency is FULL, but 'show ipv6 route ospf' on R1 shows only a default route. R2 is an ASBR redistributing connected routes into OSPFv3. 'show ipv6 ospf database external' on R1 shows the external routes, but they are not installed in the routing table. What is the most likely cause?
hard- ✓ A.The router R1 has a distribute-list in the OSPFv3 process that filters out the external routes.
- B.The external routes have a metric of 16777214, which is considered infinite.
- C.The router R1 does not have IPv6 unicast routing enabled.
- D.The external routes are type 5 LSAs but the router is in a totally stubby area.
Why A: In OSPFv3, external routes are not installed if the router has a route to the forwarding address that is not reachable. However, the more common cause is that the OSPFv3 process on R1 has 'no ipv6 unicast-routing' or the router is missing a default route to reach the external destinations. Another possibility is that the external routes have a metric that is too high or the route is suppressed by a filter. The most likely cause is that the router has a route map or distribute list that is filtering the external routes from being installed.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.